Heat exchanger

ABSTRACT

The invention relates to a heat exchanger used, in particular for motor vehicle air-conditioning systems with a liquid coolant. In a preferred variant, the used coolant is embodied in the form of carbon dioxide. The inventive heat exchanger comprises at least one supply duct, an exhaust line, two heat-exchanging units which are provided with at least one distribution space and one accumulating space and at least one circulating system. Each heat-exchanging unit is provided with at least one dividing system for dividing at least one distribution space or one accumulating space into two partial spaces. Said heat exchanger also comprises a flow actuating system connecting the heat-exchanging units to each other. The flow cross sections or the totality thereof arranged before and after said flow actuating device have a predetermined ratio therebetween.

The invention relates to an apparatus for heat exchange, in particularfor use in air-conditioning systems and especially for use inair-conditioning systems which, as refrigerant, have a fluid which has,for example, at least carbon dioxide as a constituent.

Such apparatuses for heat exchange are used, for example, to cool orcondense refrigerants.

The invention and the technical problems on which it is based will bedescribed below with reference to an example of a motor vehicleair-conditioning system. However, it should be noted that the apparatusaccording to the invention is also suitable for other intendedapplications.

The invention also relates to a process for producing an apparatus forheat exchange.

The prior art has disclosed air-conditioning systems in motor vehicles.These air-conditioning systems use a refrigerant which is used to coolair for the vehicle interior. Examples of refrigerants of this typeinclude chlorofluorocarbons. However, air-conditioning systems which areoperated with refrigerants of this type have the drawback of causing asignificant increase in the fuel consumption of a motor vehicle.Furthermore, these conventional refrigerants have a very high greenhousegas potential and consequently the use of these refrigerants alsoincreases the environmental problems caused by the greenhouse effect.For this reason, in recent times, a further refrigerant, namely carbondioxide (CO₂), has been used. Compared to the refrigerants referred toabove, carbon dioxide has a considerably lower greenhouse gas potential.Furthermore, carbon dioxide does not cause any damage to the ozonelayer, since it is a natural gas. Finally, the use of carbon dioxide asrefrigerant also makes it possible to reduce the fuel consumption of themotor vehicle.

However, when carbon dioxide is used as refrigerant, very high pressuresin the range of up to more than 130 bar have to be produced. Thepressure loading on individual components of an air-conditioning systemtherefore rises significantly, thus requiring higher stability.

The invention is therefore based on the object of providing an apparatusfor heat exchange which is improved in comparison to the prior art.

According to the invention, the object is achieved by the subject matterof main claim 1. Advantageous refinements form the subject matter of thesubclaims.

In one embodiment, an apparatus for heat exchange, in particular for-usein motor vehicles and especially for use in motor vehicleair-conditioning systems which, as refrigerant, have a fluid whichcomprises at least one constituent selected from a group of gasesconsisting in particular of carbon dioxide, nitrogen, oxygen, air,ammonia, hydrocarbons, in particular methane, propane, n-butane, andliquids, in particular water, fluids, brines, etc., has a feed line anda discharge line in order to introduce the fluid into the apparatus andto remove the fluid from the apparatus. In one particularly preferredembodiment, the refrigerant used is carbon dioxide, which isdistinguished by its physical and chemical properties, such as, forexample, noncombustibility.

Furthermore, the apparatus according to the invention for heat exchangehas at least two heat exchanger units, each of these heat exchangerunits having at least one distribution space and one collection spaceand at least one throughflow device, with it being possible for thefluid to flow between the distribution and collection spaces through thethroughflow device.

Furthermore, each of these heat exchanger units has at least oneseparating device which divides at least one distribution or collectionspace into two subspaces.

The apparatus also has a flow connection device which connects the heatexchanger units to one another in such a manner that the refrigerant canflow between the heat exchanger units, with the flow cross sections orthe flow cross section totals upstream and downstream of the flowconnection device assuming a predetermined ratio to one another. Thisratio depends in particular on the position of the flow connectiondevice.

In a further preferred embodiment, the throughflow device has at leastone first end-side flow connection section, through which the fluidenters the throughflow device or leaves the throughflow device.

Furthermore, a second end-side flow connection section is provided,through which the fluid leaves the throughflow device or enters thethroughflow device. The first flow connection section and the secondflow connection section are flow-connected to each other by at least onetube section.

In the context of the present invention, the term “flow-connected” is tobe understood as meaning that a fluid can flow between twoflow-connected sections.

In a further preferred embodiment, the tube section has at least onestraight section, and is linear (what does this mean?) preferably alongits entire length. However, in addition to straight sections, the tubesection may also have one or more curved sections.

In one particularly preferred embodiment, at least one of said end-sideflow connection sections is twisted at least once. In this context, theterm “twisting” is to be understood as meaning that a component isrotated or twisted through a defined, predetermined angle along itslongitudinal direction. In this case, the central axis may be offset.

In a further particularly preferred embodiment, the apparatus for heatexchange has in its entirety or at least the throughflow device, as acomponent of the apparatus, has a preferably gaseous medium, inparticular air, flowing around it.

Within the meaning of the present invention, a collection space is to beunderstood as meaning a device which is suitable for collecting mediumsupplied to it from at least one component, preferably a plurality ofcomponents. The distribution space is used to distribute a fluid whichis introduced into it to at least one, preferably a plurality of,devices or throughflow devices.

In a further preferred embodiment, the throughflow device has at leastone flow passage, preferably a multiplicity of flow passages, forpassing on the refrigerant, and preferably has a cross section in theform of a flat tube.

In the context of the present invention, the term in the form of a flattube is to be understood as meaning that the cross section issubstantially in the shape of a rectangle or ellipse, with the longerside of this rectangle being longer than the shorter side or the longersemi-axis being longer than the shorter semi-axis.

According to a preferred embodiment, the transitions between the sidesof the cross section are rounded.

In a further particularly preferred embodiment, a plurality of heatexchanger units are provided, which are in each case connected to flowconnection devices. The plurality of heat exchanger units are preferablyconnected in pairs in each case by flow connection devices.

In this case, the number of heat exchanger units is particularlypreferably n, and the number of flow connection devices n-1. However, itis also possible to provide a plurality of flow connection devicesbetween the individual heat exchanger units.

In a further preferred embodiment, the feed line and the discharge linefor the refrigerant are arranged at two different distribution orcollection spaces.

In a particularly preferred embodiment, the feed line and the dischargeline for the refrigerant extend along the longitudinal direction of thedistribution and collection spaces at which they are arranged.

In a further particularly preferred embodiment, a frame device isprovided which connects the individual heat exchanger units to oneanother nonpositively, positively and/or cohesively.

In a preferred embodiment, the distribution space and/or the collectionspace have receiving devices or lead-through devices, the internal crosssection of the receiving devices substantially corresponding to theexternal cross section of the throughflow device. In this case, theexternal cross section of the throughflow device is particularlypreferably slightly smaller than the internal cross section of thereceiving devices, so that the throughflow device, preferably aplurality of throughflow devices, can be pushed into the individualreceiving devices or can be pushed through them. The receiving devicemay also be designed as a lead-through device, so that the throughflowdevice is pushed through the receiving device into the collection and/ordistribution space. The receiving device may also be designed in such amanner that a plurality of flat tubes can be accommodated therein.

In a further preferred embodiment, the receiving devices aresubstantially rectangular or elliptical in form, with the longer side ofthese substantially rectangular or elliptical receiving devices beingarranged at a predetermined angle with respect to the longitudinaldirection of the distribution and collection device.

In this case, the longitudinal direction of the distribution/collectiondevice is to be understood as meaning the direction in which thedistribution/collection space substantially extends.

In a further preferred embodiment, the magnitude of this predeterminedangle between the longitudinal direction of the distribution/collectionspace is between 0 and 90 degrees, preferably between 0 and 45 degrees,and particularly preferably between 0 and 10 degrees. In this context, arotation of the receiving device in the clockwise direction with respectto the longitudinal direction is indicated by a positive angle.

In a further preferred embodiment, a plurality of throughflow devicesare arranged substantially parallel to one another. In this context, theterm parallel arrangement is to be understood as meaning that theflattened part in each case of the throughflow device which is in theform of a flat tube is substantially parallel to the flattened part ofthe other throughflow devices. In a further preferred embodiment,cooling ribs which promote heat exchange with the air flowing through oraround are provided between the throughflow devices.

Devices for heat exchange, such as, for example, cooling ribs, vanes orslats, are particularly preferably provided between the individualthroughflow devices.

In a further preferred embodiment, the flow connection device isarranged at a predetermined angle with respect to the longitudinaldirection of the distribution or collection spaces. In this case, thispredetermined angle is in the region of between 0 and 90 degrees,preferably between 0 to 45 degrees, and particularly preferably in theregion of approximately 30 degrees.

The effect achieved by the use of the separating devices and the flowconnection device is that the refrigerant does not immediately expandalong the entire length of the apparatus, but rather that therefrigerant flows through some sections of and consecutively through theindividual throughflow devices, which will be described in more detailbelow.

In one particularly advantageous embodiment, the separating device andthe flow connection device are arranged in such a manner that mediumflows firstly through a first section, remote from the air flowingthrough, then through a second section, remote from the air flowingthrough, then through a first section facing the air flowing through,and then through the second section facing the air flowing through. Asan alternative, it is also possible to allow the refrigerant to flowfirstly through the sections remote from the air and then through thesections facing the air.

This embodiment is particularly advantageous if the fluid temperatureexperiences a difference in temperature (temperature response) along theflow path, the fluid temperature decreasing along the flow path in thecase of a gas cooler which is operated in particular with a fluid (forexample CO₂) in a super-critical range. By virtue of the arrangement ofthe feed line on that part of the heat exchanger which is remote fromthe air and the arrangement of the discharge line on that part of theheat exchanger which faces the air, it is ensured that over the entireflow path of the fluid—from the inlet to the outlet—there is anoptimized operative difference in temperature between the fluid flowingthrough the heat exchanger and the air flow. In addition, thisarrangement enables all of the tubes on the output side to be directlyin contact with the cooler air flow.

In a further embodiment, the use of a plurality of separating devices inthe individual distribution and collection spaces results in theformation of a plurality of the abovementioned sections, and therefrigerant can thus be conducted through the connections morefrequently in the manner of a cross-countercurrent. Furthermore, it isalso possible to provide a plurality of flow connection devices betweentwo heat exchanger units in order thereby to conduct the refrigerant toand fro between the individual heat exchanger units more frequently.

In a further preferred embodiment, the throughflow device is producedfrom at least one material selected from a group of materials consistingof metals, in particular aluminum, manganese, silicon, magnesium, iron,brass, copper, tin, zinc, titanium, chromium, molybdenum, vanadium, andalloys thereof, in particular wrought aluminum alloys with a siliconcontent of from 0 to 0.7% and a magnesium content of between 0.0 and 1%,preferably between 0.0% and 0.5%, and particularly preferably between0.1% and 0.4%, preferably EN-AW 3003, EN-AW 3102, EN-AW 6060 and EN-AW1100, plastics, fiber-reinforced plastics, composite materials, etc.

In a further embodiment, more than one, preferably heat exchanger unitsare provided and are thermally separated from one another.

The term thermal separation is to be understood as meaning a state whichcompletely or at least substantially prevents heat transfer between thecomponents involved, i.e., for example, two heat exchanger units. In apreferred embodiment, the thermal separation of the heat exchanger unitsis achieved by the distribution space and the collection space beingspaced apart from one another, so that an air gap is formed between thespaces.

In a further embodiment, the heat exchanger units are held spaced apartby means of a frame device. It is also possible for bridge-likeconnections to be provided between the heat exchanger units in order tohold the latter spaced apart.

In a further particularly preferred embodiment, a material which effectsthermal separation between the distribution space and the collectionspace is arranged between the heat exchanger units, and the distributionspace and the collection space are cohesively connected to one anotherby means of this material.

The invention also relates to a device for exchanging heat, inparticular for motor vehicle air-conditioning systems, having air flowpaths, air flow control elements, at least one air delivery device and ahousing which is suitable for receiving at least one apparatus for heatexchange and within which such an apparatus for heat exchange isarranged.

The invention preferably relates to a device for exchanging heat, inparticular for motor vehicle air-conditioning systems, having at leastone evaporator, a compressor, an expansion valve, a collector and atleast one apparatus for heat exchange.

The invention is explained in more detail in the exemplary embodimentbelow with reference to the associated drawings, in which:

FIG. 1 diagrammatically depicts an apparatus for heat exchange inaccordance with the invention;

FIG. 2 diagrammatically depicts a throughflow device for the apparatusaccording to the invention;

FIG. 3 shows a diagrammatic plan view of a flow connection section onone side for an apparatus for heat exchange;

FIG. 4 diagrammatically depicts a collection space or a distributionspace for an apparatus for heat exchange in accordance with the presentinvention;

FIG. 4 a shows an illustration on line A-A in FIG. 4;

FIG. 5 shows a side view of the illustration shown in FIG. 1;

FIG. 6 diagrammatically depicts the flow directions in the apparatus forheat exchange from FIG. 5;

FIG. 7 shows a perspective illustration of a flow connection deviceaccording to the invention;

FIG. 7 a shows a further illustration of the flow connection deviceshown in FIG. 7; and

FIG. 7 b shows a further illustration of the flow connection deviceshown in FIG. 7.

FIG. 1 shows an illustration of an apparatus for heat exchange inaccordance with the present invention. The apparatus has a feed line 1and a discharge line 2. The feed line 1 opens into a distribution spaceor collection space 4 b in such a manner that it is flow-connected tothis space. A distribution space or collection space is to be understoodas meaning a volume element substantially delimited in the longitudinaldirection. This volume element may extend over the entire length 1 ofthe apparatus but may also be of a shorter length, for example ifseparating devices are provided. Reference numeral 7 indicates athroughflow device, through which a fluid can flow. It is preferable fora plurality of these throughflow devices 7, 7′, 7″ to be arranged in theapparatus for heat exchange. Cooling ribs 10 are provided between thesethroughflow devices.

The main flow direction of the air flowing through the apparatus or ofthe air flowing around the apparatus is substantially perpendicular tothe flow surface of the fluid in FIG. 1 and is indicated by way ofexample by the arrows P.

These cooling ribs preferably have gills (not shown in the illustration)which further promote heat exchange with the air flowing around them, inparticular by producing turbulences. The density of the cooling ribs is10 to 150 ribs per decimeter, preferably 45 to 100 ribs per decimeter,and particularly preferably 50 to 95 ribs per decimeter.

The length of the gills is from 1 mm to 20 mm, preferably between 2 mmand 15 mm, and particularly preferably from 3.5 mm to 12 mm. The widthof the slat slots is between 0.05 mm and 0.5 mm, preferably between 0.1mm and 0.4 mm, and particularly preferably between 0.2 mm and 0.3 mm.

In the illustration, the distribution or collection space 4 b, thedistribution or collection space 5 b and the throughflow device 7 orthroughflow devices 7 connecting these two distribution or collectionspaces form a heat exchanger unit. In the figure shown, there aretherefore two heat exchanger units. In this case, the heat exchangerunits may each have their own cooling ribs or common cooling ribs.

Reference numeral 11 denotes a frame device which can at least partiallybe connected positively, nonpositively and/or cohesively to thecollection space and/or the distribution space. Reference numeral 13refers to a throughflow connection device which brings two of thedistribution or collection spaces into flow connection.

(In the context of the present invention, identical in height is to beunderstood as meaning that the feed line and the discharge line arearranged along a certain direction, here at the substantially identicalheight h. Substantially identical in height is to be understood asmeaning that the distance between the feed line and the discharge linealong the direction h is smaller than the height h of the apparatus, ispreferably smaller than half of the height h of the apparatus, and isparticularly preferably smaller than 1/10 of the length of the device.)

The distribution or collection spaces 4 b and 5 b are flow-connected toone another by means of at least one, preferably a plurality of,throughflow devices 7. The throughflow device has a cross section whichis substantially in the form of a flat tube, and a flow passage or amultiplicity of flow passages for passing on the refrigerant. Theindividual flow passages are in this case substantially circular orelliptical in cross section.

The height of the individual passages is between 0.2 mm and 3 mm,preferably between 0.5 mm and 2 mm, and particularly preferably between0.6 mm and 1.8 mm.

The hydraulic diameter is between 0.1 mm and 3 mm, preferably between0.4 mm and 2 mm, and particularly preferably between 0.6 mm and 1.8 mm.

The distance between the individual throughflow devices along thedirection 1 in FIG. 1 is between 2 mm and 30 mm, preferably between 4 mmand 20 mm, and particularly preferably between 6 mm and 14 mm.

FIG. 2 diagrammatically depicts a throughflow device for an apparatusfor heat exchange in accordance with the present invention.

Reference numerals 23 and 23′ denote a first and second end-side flowconnection section. Reference numeral 26 denotes a tube section of thethroughflow device. The end-side flow connection section 23 and theend-side flow connection section 23′ are, as apparent from theillustration, in each case twisted once. In the illustration presenthere, there is a twisting through a twisting angle of 90 degrees. Inprinciple, however, twisting angles of 0 to 90 degrees in bothdirections are conceivable. In FIG. 3, the two flow connection sectionsare twisted in the same direction.

However, it is also possible for the twisting to be carried out indifferent directions.

The width b of the throughflow device is between 4 mm and 20 mm,preferably between 5 mm and 12 mm and, particularly preferably, between6 mm and 9 mm. The thickness d of the throughflow device is between 1 mmand 3 mm, preferably between 1.2 mm and 2.2 mm, and particularlypreferably between 1.5 mm and 2 mm.

FIG. 3 diagrammatically depicts the cross section through thethroughflow device 7 in the region of an end-side flow connectionsection 23. In this case, the throughflow device illustrated has aplurality of flow passages 27.

Furthermore, FIG. 3 serves to illustrate the twisting. In the exampleshown here, the throughflow device is twisted through 90° in thecounterclockwise direction in the direction of the positive z axis, i.e.is rotated through a twisting angle β of −90°. By this definition, thetwists of the two end-side flow connection sections 23 and 23′ shown inthe figure have a twisting angle with a magnitude of 90° and a negativesign of −90°.

FIG. 4 diagrammatically depicts a detail of a distribution or collectionspace. The distribution or collection space has a multiplicity ofreceiving devices 31 and 31′. These receiving devices are used toreceive and lead through the throughflow device 7. In this case, theinternal diameter of these lead-through devices substantiallycorresponds to the external cross section of the throughflow device 7 atthe end thereof and is preferably slightly greater. During production,the end sections of the throughflow device are pushed into the receivingdevices 31 and 31′ or are pushed through them. The receiving devices andthe throughflow devices are then connected fluid-tightly, for example bymeans of solder, adhesive or the like.

The connection between the throughflow devices and the receiving devicesof the collection or distribution space affords the advantage that it ispossible to absorb even the high pressures of, for example, up toapprox. 400 bar which are required in carbon dioxide coolers, and theflow paths are still gastight and/or liquid-tight even at these highpressures.

In a preferred embodiment, the depth of insertion of the throughflowdevices into the collection or distribution space is limited by thetwisting of the end-side flow connection section. However, it is alsopossible for the throughflow devices to be pushed in until the tubesstrike against the boundary walls of the distribution or collectionspace. The depth of insertion is dependent among other things on themanufacturing process, material thickness, predetermined tolerances,etc. The depth of insertion is normally between 1 mm and 25 mm,preferably between 2 mm and 15 mm, and particularly preferably between 3mm and 10 mm.

The individual receiving devices 31 and 31′ are arranged along thelongitudinal direction 1 of the receiving space and/or the collectionspace, i.e. their longitudinal direction, which is indicated by thedashed section g, and includes an angle of a magnitude of less than 10degrees, preferably substantially 0°, with the longitudinal direction 1,i.e. is parallel. However, it is also possible for the receiving devicesto be arranged at a different angle of up to 90° with respect to thelongitudinal direction.

FIG. 4 a shows a section from FIG. 4 on line A-A′. Reference numerals 35and 35′ denote the clamping walls which are used for clamping in theflow connection section. Reference numeral 31 shows the receivingdevice, which is illustrated in the form of a gap in this sectionalrepresentation. As can be seen from FIG. 4 a, the flow connectionsection has an approximately Q-shaped cross section.

FIG. 5 shows a side view of the apparatus for heat exchange inaccordance with the present invention. Reference numerals 4 a and 4 bdenote two collection and distribution spaces which are part of twodifferent heat exchanger units. In a preferred embodiment, the twocollection and distribution spaces do not directly touch one another butrather are spaced apart from one another, as indicated by referencenumeral 8. Reference numerals 1 and 2 refer to a feed line and adischarge line for the refrigerant. However, it is conceivable for thetwo heat exchanger units to use a common corrugated rib.

In a preferred embodiment, a flow connection of the collection space tothe distribution space takes place by means of the web- or bridge-likeflow connection device 13.

In this context, web- or bridge-like is to be understood as meaning thatthe flow connection does not come about exclusively within adistribution or collection device but rather substantially outside thesame, for example, in FIG. 5, it runs above the same.

In addition, separating devices 13 a and 13 b are provided, which dividethe distribution or collection spaces 4 a and 4 b into two separatesubspaces a and b or c and d in each case. The length of the subspace ais preferably smaller than the length of the subspace c and/or greaterthan or equal to the length of the subspace d. The length of thesubspace b is preferably smaller than or equal to the length of thesubspace c. The length of the subspace d is preferably smaller than thelengths of the subspaces b and/or c.

As an alternative, it is, however, possible for the flow connectiondevice 13 to also be combined with the separating devices 13 a and 13 band to be pushed into provided slots in the distribution or collectionspaces 4 a and 4 b. In this case, the separating device is preferablysoldered or welded to the distribution or collection space or isconnected fluid-tightly to the surroundings in some other way.

FIG. 7 shows a perspective illustration of a combined flow connectiondevice/separating device. In this case, reference numerals 13 a and 13 brefer to the separating elements of the device, and reference numeral 41denotes a flow connection opening.

FIGS. 7 a and 7 b show further views of the combined flow connectiondevice/separating devices shown in FIG. 7.

With reference to FIGS. 5 and 6, the flow paths in the apparatus forheat exchange will be explained below in accordance with thisembodiment.

The refrigerant first of all passes via the feed line 1 into the spacesection a of the distribution or collection space 4 b. It can extendthere along the longitudinal direction 1 of the distribution orcollection space 4 b as far as the separating device 13 b. From there,the refrigerant flows downward via the throughflow devices 7, 7′, 7″ . .. (not shown), i.e. onto the plane of the sheet in the drawing, which isillustrated by the x symbols. In the arrow diagram shown in FIG. 4, thisis illustrated by the solid, downwardly pointing arrows in the rightpart of the drawing.

The lower distribution or collection space 5 b does not have aseparating device, and so the refrigerant can extend here along theentire length thereof. In this case, the right part of this spacetherefore acts as a collection space and the left part as a distributionspace. This is expressed in FIG. 6 by the fact that the line symbolizingthe distribution or collection space 5 b is not depicted in interruptedform.

From the left section of the lower distribution or collection space 5 b,the refrigerant flows upward again through the throughflow devices,which is symbolized by the solid, upwardly directed arrows on the leftside of FIG. 4. The refrigerant passes into the section denoted by b inFIG. 5. This is indicated in the figure by the symbols provided with thedot.

From the subspace b, the refrigerant flows via the flow connectiondevice 13 into the subspace, denoted by c, of the distribution andcollection space 4 a. The refrigerant passes via the throughflow devicesinto the lower distribution/collection space 5 a (shown in FIG. 6), i.e.the refrigerant flows in FIG. 5 in a direction perpendicular withrespect to the plane of the sheet, which is illustrated by the x symbolsin FIG. 5 and by the downwardly directed, dashed arrows in FIG. 6. Inthe lower distribution/collection space, the refrigerant again extendsalong the entire length thereof and finally passes again via thethroughflow devices into the section d of the distribution andcollection space 4a. From there, the refrigerant flows out of theapparatus via the discharge line 2.

The effect achieved by this construction is that the refrigerant firstlyflows through substantially all of the throughflow devices of a heatexchanger unit and subsequently through substantially all of thethroughflow devices of the second heat exchanger unit. The effect isalso achieved that the refrigerant does not flow through the throughflowdevices of a heat exchanger unit at substantially the same time, butrather section by section, with the sections being determined by theseparating devices. This enables a more uniform cooling of thecirculating medium to be achieved over the entire area of thethroughflow devices.

Furthermore, it is also possible for a plurality of separating devicesand/or a plurality of throughflow devices to be provided in order toachieve the effect that medium will flow through the apparatus or theheat exchanger units in a plurality of sections. A relatively largenumber of flow connection devices may also be used to arrange more thantwo heat exchanger units one behind another.

1. An apparatus for heat exchange, in particular for use in motorvehicles and especially for use in motor vehicle air-conditioningsystems which have a fluid as refrigerant, at least one feed line anddischarge line (1, 2) in order to introduce the fluid into the apparatusand to remove the fluid from the apparatus; at least two heat exchangerunits, each of these heat exchanger units having at least onedistribution space or one collection space (4 a, 5 a, 4 b, 5 b) and atleast one throughflow device (7), with it being possible for the fluidto flow between the at least two distribution or collection spaces (4 a,5 a, 4 b, 5 b) through the throughflow device (7), and at least oneseparating device (1 3a) which divides at least one distribution orcollection space into two subspaces, at least one flow connection device(13) which connects the heat exchanger units to one another in such amanner that the refrigerant can flow between the heat exchanger units,with the flow cross sections upstream and downstream of the flowconnection device assuming a predetermined ratio to one another.
 2. Theapparatus for heat exchange, in particular as claimed in claim 1,characterized in that the throughflow device (7) has at least one firstend-side flow connection section (23), through which the refrigerantenters the throughflow device (7) or leaves the throughflow device (7),and a second end-side flow connection section (23′), through which therefrigerant leaves the throughflow device (7) or enters the throughflowdevice (7), and in that the first flow connection section (23) and thesecond flow connection section (23′) are flow-connected to each other byat least one tube section (26).
 3. The apparatus for heat exchange, inparticular as claimed in claim 1, characterized in that the tube section(26) has at least one straight section.
 4. The apparatus for heatexchange, in particular as claimed in claim 1, characterized in that thetube section (26) has at least one curved section.
 5. The apparatus forheat exchange, in particular as claimed in claim 1, characterized inthat at least one flow connection section (23, 23′) has a twistedsection.
 6. The apparatus for heat exchange, in particular as claimed inclaim 1, characterized in that the throughflow device has at least oneflow passage (27), preferably a plurality of flow passages, for passingon the refrigerant.
 7. The apparatus for heat exchange, in particular asclaimed in claim 1, characterized in that a plurality of throughflowdevices (7) are provided and devices for heat exchange, such as, forexample, cooling ribs (10), are provided between these throughflowdevices (7).
 8. The apparatus for heat exchange, in particular asclaimed in claim 1, characterized in that the throughflow device (7) hasa cross section in the form of a flat tube.
 9. The apparatus for heatexchange, in particular as claimed in claim 1, characterized in that theheat exchanger units are preferably connected in pairs by flowconnection devices (13).
 10. The apparatus for heat exchange, inparticular as claimed in claim 1, characterized in that the number ofheat exchanger units is n and the number of flow connection devices isn-1.
 11. The apparatus for heat exchange, characterized in that aplurality of separating devices (13 a, 13 b) are provided, which dividethe distribution or collection spaces into a plurality of subspaces. 12.The apparatus for heat exchange, in particular as claimed in claim 1,characterized in that the feed line (1) and the discharge line (2) forthe refrigerant are arranged at different distribution or collectionspaces (4 a, 4 b).
 13. The apparatus for heat exchange, in particular asclaimed in claim 1, characterized in that the feed line (1) and thedischarge line (2) for the refrigerant extend along the longitudinaldirection of the distribution or collection spaces (4 a, 4 b) at whichthey are arranged.
 14. The apparatus for heat exchange, in particular asclaimed in claim 1, characterized in that the individual heat exchangerunits are connected nonpositively, positively and/or cohesively to oneanother, in particular by a frame device (11).
 15. The apparatus forheat exchange, in particular as claimed in claim 1, characterized inthat at least the first and/or the second flow connection section (23,23′) is twisted over a predetermined angle.
 16. The apparatus for heatexchange, in particular as claimed in claim 1, characterized in that themagnitude of the twisting angle is between 10° and 180°, preferablybetween 45° and 135°, and particularly preferably between 80° and 100°.17. The apparatus for heat exchange, in particular as claimed in claim1, characterized in that at least one of the distribution and collectionspaces has receiving devices (31), the internal cross section of thereceiving devices (31) substantially corresponding to the external crosssection of the throughflow device (7).
 18. The apparatus for heatexchange, in particular as claimed in claim 1, characterized in that thereceiving devices (31) are substantially rectangular in form, and thelonger side of these receiving devices (31) is arranged at apredetermined angle with respect to the longitudinal direction of thedistribution and collection spaces (4 a, 4 b, 5 a, 5 b).
 19. Theapparatus for heat exchange, in particular as claimed in claim 1,characterized in that the magnitude of the angle is between 0 degreesand 90 degrees, preferably between 0 degrees and 45 degrees, andparticularly preferably between 0 degrees and 10 degrees.
 20. Theapparatus for heat exchange, in particular as claimed in claim 1,characterized in that a plurality of throughflow devices (7) arearranged substantially parallel to one another.
 21. The apparatus forheat exchange, in particular as claimed in at least one of the precedingclaims claim 1, characterized in that the throughflow device (7) isproduced from at least one material selected from a group of materialsconsisting of metals, in particular aluminum, manganese, silicon,magnesium, iron, brass, copper, tin, zinc, titanium, chromium,molybdenum, vanadium, silicon, magnesium and alloys, such as EN-AW 3003,EN-AW 3102, EN-AW 6060, EN-AW 1110 thereof, plastics, fiber-reinforcedplastics, composite materials.
 22. The apparatus for heat exchange, inparticular as claimed in claim 1, characterized in that more than one,preferably two heat exchanger units are provided and are thermallyseparated from one another.
 23. The apparatus for heat exchange, inparticular as claimed in claim 1, characterized in that at least twoheat exchanger units are held spaced apart by means of a frame device(11).
 24. The apparatus for heat exchange, in particular as claimed inclaim 1, characterized in that a material which effects thermalseparation between the heat exchanger units is arranged between at leasttwo heat exchanger units, and the heat exchanger units are cohesivelyconnected to one another by means of this material.
 25. An apparatus forexchanging heat, in particular for motor vehicle air-conditioningsystems, having air flow paths, air flow control elements, at least oneair delivery device and a housing which is suitable for receiving atleast one apparatus for heat exchange, in particular as claimed in claim1, or within which such an apparatus for heat exchange is arranged. 26.A device for exchanging heat, in particular for motor vehicleair-conditioning systems, having at least one condenser, a compressor,an expansion valve, a collector and at least one apparatus for heatexchange, in particular as claimed in claim 1.